Background It is unclear whether the reported variation in the diagnosis of intraductal carcinoma of the prostate (IDC-P) is due to variable interpretation of borderline morphology, use of different diagnostic criteria or both.

Aims We sought to determine the degree of variation in the diagnostic criteria and reporting rules for IDC-P in prostate biopsies employed by expert uropathologists.

Methods A questionnaire survey was circulated to 23 expert uropathologists from 11 European countries.

Results Criteria used for diagnosis of IDC-P included solid intraductal growth (100%), dense cribriform (96%), loose cribriform/micropapillary with nuclear size >6× normal (83%) or comedonecrosis (74%) and dilated ducts >2× normal (39%). ‘Nuclear size’ was interpreted as nuclear area by 74% and nuclear diameter by 21%. Pure IDC-P in needle biopsies was reported by 100% and Gleason graded by 30%. All would perform immunohistochemistry in such cases to rule out invasive cancer. An IDC-P component associated with invasive cancer would be included in the determination of tumour extent and number of cores involved by 74% and 83%, respectively. 52% would include IDC-P component when grading invasive cancer. 48% would perform immunohistochemistry in solid or cribriform nests with comedonecrosis to exclude IDC-P (17% routinely, 30% if the focus appeared to have basal cells on H&E). 48% graded such foci as Gleason pattern 5 even if immunohistochemistry demonstrated the presence of basal cells.

Conclusions There is a need for more clarity in the definition of some of the diagnostic criteria for IDC-P as well as for greater standardisation of IDC-P reporting.